As a heat-absorbing glass plate for an automobile, one comprising soda lime silica glass which is green or blue by containing coloring components has been known.
A heat-absorbing glass plate is required to have a low solar transmittance (for example, a solar transmittance (hereinafter sometimes referred to as Te) of at most 42% calculated as 4 mm thickness as identified in JIS R3106 (1998)) and a high visible light transmittance (for example, a visible light transmittance (hereinafter sometimes referred to as Tv) (by illuminant A) of at least 70% calculated as 4 mm thickness as defined in JIS R3106 (1998)).
Further, as a heat-absorbing glass plate, a green heat-absorbing glass plate which provides a more natural color tone of a transmitted light when a passenger looks out of window through the glass plate, tends to be preferred.
Further, for a heat-absorbing glass plate, with a view to suppressing inclusion of impurities when the glass base (kind of glass) is changed in a melting furnace to be used for production of glass and in view of the cost, it is required that the number of the coloring components is reduced as far as possible, and that the unit price of the material of the coloring component is low.
As a heat-absorbing glass plate, for example, the following (1) to (3) have been proposed.    (1) A heat-absorbing glass plate (Patent Document 1) comprising soda lime silica glass which contains, as coloring components, as represented by mass % based on oxides:
total iron as calculated as Fe2O3: 0.3 to 0.7%,
CeO2: 1.7 to 2.5%,
SO3: 0.01 to 0.1%,
TiO2: 0 to 1% and
MnO2: 0 to 1%,
which contains substantially no Se, NiO nor CoO, and which has a mass ratio of FeO/total Fe2O3 of from 0.26 to 0.60.    (2) A heat-absorbing glass plate (Patent Document 2) which comprises soda lime silica glass having a Redox of from 0.38 to 0.60,    containing from 0.005 to 0.18% of SO3 as represented by mass % based on oxides, and    containing substantially no polysulfide, and    which contains, as coloring components, any one of I) to V) as represented by mass % or by mass ppm:    I) total iron as calculated as Fe2O3: 0.6 to 4%,
FeO: 0.23 to 2.4%,
CoO: 40 to 500 ppm,
Se: 5 to 70 ppm,
Cr2O3: 15 to 800 ppm,
TiO2: 0.02 to 1%.    II) total iron as calculated as Fe2O3: 0.4 to 1%,
CoO: 4 to 40 ppm,
Cr2O3: 0 to 100 ppm.    III) total iron as calculated as Fe2O3: 0.9 to 2%,
FeO: 0.34 to 1.2%,
CoO: 90 to 250 ppm,
Se: 0 to 12 ppm,
TiO2: 0 to 0.9%.    IV) total iron as calculated as Fe2O3: 0.7 to 2.2%,
FeO: 0.266 to 1.32%,
Se: 3 to 100 ppm,
CoO: 0 to 100 ppm.    V) total iron as calculated as Fe2O3: 0.9 to 2%,
FeO: 0.34 to 1.2%,
CoO: 40 to 150 ppm,
Cr2O3: 250 to 800 ppm,
TiO2: 0.1 to 1%.    (3) A heat-absorbing glass plate (Patent Document 3) which comprises soda lime silica glass containing, as coloring component, as represented by mass % or mass ppm based on oxides:
total iron as calculated as Fe2O3: 0.45 to 0.65%,
bivalent iron as calculated as FeO: 0.23 to 0.28% and
CoO: 0 to 3 ppm, and
having a mass ratio of FeO/total Fe2O3 of from 0.35 to 0.55.
Although the heat-absorbing glass plate (1) is green, it does not satisfy both Te≦42% (calculated as 4 mm thickness) and Tv≧70% (calculated as 4 mm thickness). Further, it contains a large amount of CeO2 in addition to TiO2 as the coloring component, and accordingly there are problems of inclusion (as described hereinafter) of impurities when the glass base is changed and the cost.
Some of heat-absorbing glass plates (2) satisfy Te≦42% (calculated as 4 mm thickness) and Tv≧70% (calculated as 4 mm thickness), they are blue. Further, it contains a large number of coloring components, and accordingly there are problems of inclusion of impurities when the glass base is changed and the cost.
Some of heat-absorbing glass plates (3) satisfy Te≦42% (calculated as 4 mm thickness) and Tv≧70% (calculated as 4 mm thickness), they are blue. Further, when such a heat-absorbing glass plate contains CoO, there is a problem of inclusion of impurities when the glass base is changed, since CoO makes the glass blue even with a small amount.
As described above, it has been difficult to obtain a heat-absorbing glass plate which satisfies Te≦42% (calculated as 4 mm thickness) and Tv≧70% (calculated as 4 mm thickness), the transmitted light through which is green, and which contains a small number of coloring components.